This application claims priority to Japanese Patent Application No. P2000-286842 and P2000-328405.
1. Field of the Invention
This invention concerns a thin layer magnetic head used for recording and reproduction, for example, in a magnetic disk storage apparatus and a magnetic disk storage apparatus mounting the magnetic head.
2. Description of the Background
In a magnetic disk storage apparatus, data on the recording media is read and written by a magnetic head. In order to increase the recording capacity per unit area of the magnetic disk, it is necessary to increase the area recording density. However, the area recording density of existing in-plane recording systems can not be increased as the length of bits to be recorded is decreased because of thermal fluctuation in the magnetization of the media.
A perpendicular recording system which records magnetization signals in a direction perpendicular to a medium is adapted to address this problem. In the perpendicular recording system, a magnetoresistive head (xe2x80x9cMR headxe2x80x9d) and a giant magnetoresistive head (xe2x80x9cGMR headxe2x80x9d) with a larger read output than non-perpendicular systems can be used for reading. However, a single pole head must to be used for the writing head in these systems. With perpendicular recording, it may be necessary to improve the track density and the linear recording density in order to improve the recording density. To improve the track density, the track width of the magnetic head is decreased and formed with higher accuracy.
In a perpendicular recording system, the shape of the main pole of the single pole type recording head has a significant effect on the magnetization pattern of the media. Specifically, the shape of the upper end face of the main pole, which is the end face of the main pole on the side opposite to the MR head (on the trailing side), greatly affects the shape of the magnetization pattern of the media. For example, JP-10-320720/1998 discloses the structure of a single pole type head having a main pole of a trapezoidal shape flattened at the upper end face and wider on the side of the MR head.
However, in the description in JP-10-320720/1998, a description is made of side recording tracks defined by the slope on both sides of the trapezoidal shape. These side recording tracks reduce cross talk with adjacent recording tracks, however, they hinder the improvement of the track density which therefore hinders any improvement in the area recording density. In such a magnetic disk storage apparatus, a skew angle is formed when the magnetic head scans from the inner circumference to the outer circumference of a disk, in which the trapezoidal pole shape erases signals on adjacent tracks. JP-10-320720/1998 has no specific descriptions about the pole forming method.
By using a polishing method, the upper surface of the main pole (second pole) can be flattened. However, when a polishing method such as chemical mechanical polishing (CMP) is used, it is difficult to control the layer thickness which hinders the accuracy of the layer thickness. The thickness may vary by as much as about xc2x10.5 xcexcm. This inaccuracy scatters the layer thickness of the main pole, thereby causing scattering in the intensity of the magnetic field from the main pole. Accordingly, it is preferred to adopt a flattening method for the upper surface of the main pole having improved controllability (accuracy) for the layer thickness.
In view of the above, the present invention preferably provides a magnetic head for perpendicular recording having a main pole of a shape with no side recording which does not erase signals on adjacent tracks caused by a skew angle. The invention also includes a manufacturing method of the magnetic head and a magnetic disk storage apparatus mounting the magnetic head for perpendicular recording.
A single pole type recording head for perpendicular recording in accordance with at least one preferred embodiment of the present invention comprises a first pole (auxiliary pole), a second pole (main pole) and a gap layer formed between the first and second poles in which the width of the first pole opposed to the gap layer is larger than the width of the second pole opposed to the gap layer. When defining the surface of the second pole opposed to the gap layer as a xe2x80x9clower layerxe2x80x9d and the surface of the second pole on the side opposite the lower surface (that is, on the trailing side) as an xe2x80x9cupper surfacexe2x80x9d which is flat, the width (B) of the lower surface is preferably smaller than the width (A) of the upper surface in the second pole. Further, an angle formed between the upper surface and both lateral (side) surfaces of the second pole is an acute angle. In accordance with this invention, a magnetic disk storage apparatus is formed by mounting the magnetic head.
In at least one preferred embodiment, the second pole has a shape in which the size changes continuously (i.e., linearly) from the width for the upper surface to the width for the lower surface of the second pole, and each lateral side of the second pole is desirably formed as a slope. In a preferred embodiment, the angle formed between the upper surface and both lateral sides to the upper surface of the second pole is within a range of approximately 60xc2x0 to 90xc2x0. Further, the upper surface of the second pole may be characterized with a xe2x80x9cflatnessxe2x80x9d that varies by less than about 30 nm between the end and the central portion in the upper surface.
In accordance with this invention, a second pole (main pole) is preferably formed by a process characterized by the following sequential steps: forming a resist pattern on an inorganic insulating layer; etching the inorganic insulating layer using the resist pattern as a mask thereby forming a groove having a bottom surface larger than the upper surface and having a slope portion; removing the resist pattern; forming a magnetic layer on the inorganic insulating layer including the groove; and flattening the magnetic layer. The second pole (main pole) may also be formed by a method, following the step of removing the resist pattern, including the sequential steps of: forming a stopper layer for chemical mechanical polishing (CMP) on the inorganic insulating layer; forming a plated underlayer on the stopper layer; plating a magnetic layer on the plated underlayer; and polishing the magnetic layer by chemical mechanical polishing (CMP).
Alternatively, the second pole (main pole) may also be formed by a method, following the step of removing the resist pattern, including the sequential steps of: forming an etching stopper layer on the inorganic insulating layer; forming a plated underlayer on the stopper layer; plating a magnetic layer on the plated underlayer; and flattening the magnetic layer by etching using plasmas.
The inorganic insulating layer is preferably a single layer comprising Al2O3, AlN, SiC, Ta2O5, TiC, TiO2 or SiO2, or a laminate or mixed layer comprising two or more of the compounds described above. The magnetic layer constituting the second pole is preferably made of a material having a saturation magnetic flux density (Bs) of at least 1.5 tesla (T). The stopper layer for chemical mechanical polishing (CMP) may be a single layer comprising C, Ta, Mo, Nb, W or Cr, or a laminate layer or an alloy layer comprising the elements described above. The etching stopper layer may be a single layer comprising Cr, Ni, Au, Pt, Pd, Ru, Rh, Cu, Ag, Tc, Re, Os or Ir or a laminate layer or an alloy layer comprising the elements described above.
In order to cope with a narrowed track of the recording head, the width (A) for the upper surface of the second pole (main pole) is preferably 0.3 xcexcm or less.
In the present invention, the second pole (main pole) of the magnetic head for perpendicular recording has a structure shape that can preferably prevent writing to and erasing adjacent tracks caused by the skew angle in the lateral sides of the second pole. Initially, for preventing writing from the lateral side of the second pole into the adjacent tracks, the shape of the second pole as viewed from the magnetic recording medium opposed surface (air bearing surface) may be an inverted tapered shape. It is also possible by forming the shape of the second pole in this way to prevent a portion of the second pole from extending over the area of adjacent tracks and erasing the data on the adjacent tracks because of the skew angle.
The tapered angle of the inverted tapered shape depends on the skew angle, and the angle xcex8 relative to the normal line direction to the upper surface of the second pole is preferably defined as 0xc2x0 less than xcex8xe2x89xa630xc2x0. That is, the angle between the upper surface and both of the lateral sides to the upper surface of the second pole is preferably set within a range of 60xc2x0 to 90xc2x0. Further, the shape of the tapered portion is preferably changed linearly from the width (A) for the upper surface to the width (B) for the lower surface.
Because the tapered angle thus formed may result in a lowering of the magnetic field intensity from the main pole, it may be necessary to increase the saturation magnetic flux density (Bs) of the main pole to at least Bs=1.5 T (tesla). Materials to accomplish this may include, for example, FeNi and CoNiFe.
As described above, both of the problems of writing into the sides and erasure of data on the adjacent tracks can be addressed by making the shape of the lateral sides of the main pole as viewed from the air bearing surface into an inverted tapered shape. Further, the upper surface of the main pole can be provided with favorable controllability for the layer thickness while flattening the upper surface by preliminarily etching a groove into the inorganic insulating layer, forming a magnetic layer in the groove and then removing any unnecessary portion by a polishing method or etching. For the inorganic insulating layer, a single layer comprising Al2O3, AlN, SiC, Ta2O5, TiC, TiO2 or SiO2, or a mixed or a laminate layer comprising the compounds as are known in the art can be adopted.
The flatness for the surface of the main pole is preferably such that a difference in thickness (flatness or smoothness) between the end and the central portion of the main pole is no more than about 30 nm. Chemical mechanical polishing (CMP) or a similar method can be used for the polishing method, and the controllability of the layer thickness can be improved by forming a stopper layer for CMP before polishing. As the stopper layer, a single layer comprising C, Ta, Mo, Nb, W or Cr or a laminate layer or an alloy layer comprising the element can be used.
When flattening is conducted by an etching method, the controllability of the layer thickness can be improved by forming an etching stopper layer before etching. As the etching stopper layer, a single layer comprising Cr, Ni, Au, Pt, Pd, Ru, Rh, Cu, Ag, Tc, Re, Os or Ir, or a laminate layer or an alloy layer containing the element is preferred. Since the track width can be determined as the size of the resist pattern formed initially, the present method can preferably improve the accuracy for if the fabrication of the track width and may be particularly effective when a magnetic head with a track width of 0.3 xcexcm or less is formed.
Fabricating the shape of the main pole in an inverse tapered shape as described above may cause additional problems in the magnetic head. FIG. 1A shows a schematic view of the magnetic head of one embodiment of the invention, as viewed from the air bearing surface. In FIG. 1A, xcex1 is an angle formed between the oblique side of the trapezoidal main pole 1 and the track running direction. When the shape of the air bearing surface of the main pole is made trapezoidal, the recording magnetic field density is decreased. FIG. 1B shows the relationship between the maximum magnetic intensity of the main pole having a trapezoidal air bearing surface and the angle xcex1. It can be seen in FIG. 1B that the magnetic field intensity decreases as xcex1 increases.
Further, JP-12-76333/2000 describes a technique of preventing erasure of data on adjacent tracks by removing a portion of the magnetic pole of the writing head thereby reducing the extension of the magnetic pole to the adjacent tracks. However, the magnetic field intensity of the head is also decreased in this case. Because the problem of thermal fluctuation becomes non-negligible as the size of the recording pit decreases, the coercive force of the medium tends to be increased as a countermeasure for thermal fluctuation. Since the recording magnetic field of the head is required to have a sufficient size to be capable of conducting recording to the medium, a decrease in the recording magnetic field intensity is disadvantageous to any improvement of the area recording density.
The erasure of data on adjacent tracks caused by the skew angle may be addressed without decreasing the recording magnetic field intensity by shaping the single pole type recording head so as to have a slope at the upper end of the main pole. In the single pole type recording head according to the present invention, the surface of the main pole situated xe2x80x9cupstreamxe2x80x9d in the rotational direction of a recording medium opposed by the writing head, (that is, on the leading side) is slanted relative to the air bearing surface of the main pole. In other words, a tapered surface is formed at the upper end of the main pole. When the tapered surface is formed as described above, the magnetic recording intensity generated may be increased when compared with a similar device without such a taper.
In addition to the increase in the recording magnetic field, the generated recording magnetic field can be concentrated or focused by optimizing the slant of the tapered surface to the air bearing surface of the main pole. Specifically, the angle of the tapered surface relative to the main pole air bearing surface (hereinafter referred to as xe2x80x9cthe angle at the upper end of the main polexe2x80x9d) is defined as between 45xc2x0 and 75xc2x0. The tapered surface may also be disposed on the trailing side instead of the leading side of the main pole. Further, the tapered surface may be disposed on both the trailing side and the leading side.
Manufacturing methods for the main pole having a tapered surface include at least the following three methods. A first manufacturing method preferably comprises the following successive steps: forming a resist pattern on an inorganic insulating layer; etching the inorganic insulating layer using the resist pattern as a mask thereby forming a slope; removing the resist pattern; forming a resist pattern on the inorganic insulating layer; forming a magnetic layer on the inorganic insulating layer; removing the resist pattern; and a step of polishing to flatten the magnetic layer. A polishing method such as chemical mechanical polishing or other appropriate methods may be used.
A second manufacturing method preferably includes the sequential steps of: forming a tapered surface by a so-called lift off method which comprises forming a resist pattern on an inorganic insulating layer, sputtering the inorganic insulating layer and removing the resist pattern, the inorganic insulating layer deposited thereto thereby forming a slope; forming a resist pattern on the inorganic insulating layer forming a magnetic layer on the inorganic insulating layer; removing the resist pattern; and polishing to flatten the magnetic layer.
A third manufacturing method preferably comprises the steps of forming a resist pattern on a magnetic layer and then etching the magnetic layer using the resist pattern as a mask to thereby form a slope.
By manufacturing the main pole as described above, it may be possible to provide a single magnetic pole type recording head that does not erase data on adjacent tracks, while preventing a decrease in the magnetic field intensity. Further, it may be possible to provide a magnetic recording apparatus with a higher area recording density that is superior in thermal fluctuation resistance to conventional apparatuses. This apparatus may be used in a longitudinal recording system by mounting a double layered perpendicular medium having a soft magnetic underlayer and a single pole type recording head.